A charge `+2q` moves vertically upwards with speed `v`, a second charge `-q` moves horizontally to the right with the same speed `v`, and a third charge `+q` moves horizonatlly to the right with the same speed `v`. The point `P` is located a perpendicular distance a away from each charge as shown in the figure. The magnetic field at point `P` is

Options

A. Into the page with magnitude `(mu_(0))/(4pi)(2qv)/(a^(2))`
B. Into the page with magnitude `(mu_(0))/(4pi)(4qv)/(a^(2))`
C. Out of the page with magnitude`(mu_(0))/(4pi)(2qv)/(a^(2))`
D. Out of the page with magnitude`(mu_(0))/(4pi)(4qv)/(a^(2))`

Answer

D

Explanation

`underset(B)(rarr)_(p)=underset(B)(rarr)_(q)+underset(B)(rarr)_(2q)+underset(B)(rarr)_(-q)`
`(mu_(0))/(4pi)(qv)/(a^(2))o.+(mu_(0))/(4pi)(2qv)/(a^(2))o. + (mu_(0))/(4pi)(qv)/(a^(2))o.`
`(mu_(0))/(4pi)(4qv)/(a^(2))o.`